I have been increasingly leaning toward wool as my favorite hunting clothing, after a brief affair with synthetics. I think the ideal is a windproof layer and good, heavy wool, like KOM or SI or GWW. We haven't had a really cold winter this year, but I was able, on the coldest days (maybe 20 degrees +/- at dawn, windy)to get away with my KOM bibs over fleece longjohns and top, and a wool hoody lined with windproof material over a wool vest. Cozy, not bulky. My only other preference, for mid season, is Berber fleece from Cabelas. Down is light and warm, but useless when wet, and it's ALWAYS wet out there, one way or another.....